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Abstract

Lettuce as an important vegetable crop warrants special research and attention. Because of environmental and economic concerns, it is necessary to determine the most efficient application levels of irrigation water and nitrogen fertilizer to achieve the optimum yield in this crop. Two field experiments were conducted to test the effect of deficit irrigation and nitrogen fertilizer applications on agronomic growth characteristics of lettuce. Experimental treatments were arranged in split strip plots based on a completely randomized block design with three replications. The irrigation and nitrogen treatments were considered at four levels (0, 25, 50, and 100% of the currently recommended water and N fertilizer for lettuce production). Results showed that 50% of irrigation water and 25% of nitrogen (IR50N25) treatment currently recommended for lettuce production led to significantly higher water (4.4 Kg DM/m3) and N (45 kg DM/kg N) use efficiencies for the fall experiment in 2017. The same results for water of 3.9 kg DM/m3 and N of 73.1 kg DM/kg were achieved in the spring experiment 2018. The optimum lettuce biomass yield was obtained for IR50N25 treatment in both experiments.